2. Field of the Invention
The present invention relates to machines for load testing lifting accessories, lifting equipment, and other tension carrying devices, and more particularly relates to an improved tension load testing machine that can adjust to fit the length of the accessory being tested in both stretched and relaxed positions, and wherein loading preliminarily stretches the accessory and thereafter tests load capability up to several thousand tons.
1. General Background
In various fields of construction and technology, heavy cranes, draglines, booms and like lifting devices are used for fabrication, construction and installation purposes. An example is the offshore oil and gas industry wherein large pre-fabricated oil rigs, platforms and production equipment are constructed in a fabrication yard and then lifted for placement on a site offshore.
In the petrochemical industry, cranes lift large vessels and prefabricated packages of several hundreds or thousands of tons. In the marine industry, large boats are lifted using cranes and the like.
Each of the various lifting environments normally involves a "package" to be lifted that is worth a great deal of money. Several millions of dollars can be lost if a large package is dropped or damaged during a lift. Typically, lifting accessories such as slings, shackles, and rigging are rated for a given load. However, it would be desirable to know that a sling, shackle, or like lifting accessory did in fact have the ability to actually hold a given load. This is especially true of older accessories that have been subjected to numerous loadings already.
One commercial machine used for loading, testing, or "proof loading" is described in brochures of Yarbrough Cable Service, Inc. of Memphis, Tenn. The Yarbrough machine is described in the Yarbrough brochure as being able to proof load to three million pounds (3,000,000) and up to two hundred feet (200') in length. The Yarbrough device employs hydraulic cylinders, and an elongated structural frame having longitudinal and transverse beam portions.